1. Field of the Invention
The invention relates to a method for applying a shrink sleeve to the closure end of a conveyed container and an apparatus for performing such a method.
2. Description of the Related Art
Apparatus for applaying shrink sleeves to the closure ends of containers are employed for safely securing the closure of beverage bottles, the thus applied shrink sleeves permitting the user to ascertain whether or not a bottle has already been opened. To this purpose a shrink sleeve is mounted on the closure end of the bottle, i.e. cn the upper end of the bottleneck, so as to surround the closure member, for instance a threaded cap or a snap-fit plug, and a portion of the bottle neck. The sleeve is then caused to shrink by the action of heat to thereby safely secure the closure member to the bottle neck. The bottle can then only be opened by breaking the shrink sleeve. It is thus always possible to ascertain whether or not a bottle has already been opened.
A method and apparatus of the type defined above are known for instance from U.S. Pat. No. 3,738,210.
In the known apparatus a hose from which the shrink sleeves are cut is unreeled from a supply drum on which the hose is wound in a flat-folded state. After the hose has been unreeled from the supply drum it is guided over an expansion mandrel. In the known apparatus the mandrel is disposed at a vertical position; the neck of the bottle to be sealed is positioned below the mandrel, whereupon a gripper is operated to pull the hose downwards by a length corresponding to the desired height of the shrink sleeve, the lower end of the hose being slipped onto the bottle neck and subsequently cut off.
In this manner it is possible to ensure a relatively accurate positioning of the shrink sleeve. A disadvantage, however, lies in the intermittent operation of this apparatus requiring the bottle conveyor means to be stopped while the shrink sleeve is being applied. The gripper is likewise operated in an intermittent manner, resulting in a complicated operating mechanism. This intermittent operation prevents a high productivity from being obtained.
Embodiments of apparatus operating in a similar manner are also known from U.S. Pat. No. 2,765,607 and U.S. Pat. No. 3,594,975.
Additionally known from EP-OS 104,292 is an apparatus for applying shrink sleeves to bottle necks in a continuous operation without requiring the bottle conveyor means to be stopped as the sleeves are being applied. In this apparatus the collapsed hose is folded out and subsequently folded again with the original fold lines in superimposed alignment. In the thus folded state the hose is passed through a pair of cutting cylinders operable to cut individual shrink sleeves from the hose across its length. The thus cut shrink sleeves are passed on through a divergent guide component engaging their outer surfaces, in which the refolded state of the sleeves causes them to be unfolded to a substantially trapezoidal shape, permitting their leading edges to be engaged by the neck of the advancing bottle and to be slipped onto the closure end.
Although this known apparatus is capable of continuous operation, the plastic hose material from which the shrink sleeves are to be cut is required to have a wall thickness of at least 75 .mu.m, since the resilient return force of the folded sleeve has to be sufficient for ensuring its unfolding to the trapezoidal shape.
In addition, the shrink sleeve has to have a determined minimum length for permitting it to be safely guided onto the bottle neck after having been cut off. Finally the cutting operation by means of the cutting cylinders may result in the opposed walls of the hose sticking together due to the pressure acting thereon, so that the required opening or unfolding of the sleeves for their application to respective bottle necks is prevented.
It is therefore an object of the invention to improve a method and apparatus of the type defined above in such a manner that the application of shrink sleeves of reduced height and formed of a thin-walled hose material can be accomplished at high operating speeds.